Introduction to the Human Body

• Anatomy– the study of the structure of

body parts and their relationships to one another

• Physiology– the study of the function of

the body’s structural machinery

Levels of Organization• Chemical• Cellular• Tissue• Organs• System Level• Organismic Level

Levels of Structural Organization• Chemical Level

– atomic and molecular level

• Cellular level– smallest living unit of the body

• Tissue level– group of cells and the materials surrounding them

that work together on one task– 4 basic tissue types

• epithelium, muscle, connective tissue, and nerve

Levels of Structural Organization

• Organ level– grouping of 2 or more tissue types into a

recognizable structure with a specific function.

• Organ system– collection of related organs with a common function– sometimes an organ is part of more than one system

• Organismic level– one living individual

Integumentary SkeletalMuscularNervousEndocrine

DigestiveCardiovascularLymphatic and ImmuneRespiratoryUrinaryReproductive

Organ Systems

Life Processes

• Metabolism = sum of all chemical processes– breakdown of large molecules into small – building new structural components (proteins)– providing chemical energy for cells

• Responsiveness– detect & respond to changes in internal or external

environment– some typical responses

• muscle contraction, electrical signals, hormone or glandular secretion

Life Processes• Movement at any structural level

– the body, an organ, a cell or cell component

• Growth– increase in number or size of cells or the material found

between cells

• Differentiation– specialization of cells for a specific function– stem cells give rise to cells that specialize

• Reproduction– formation of new cells or new individuals

Homeostasis

• Maintaining the internal environment within physiological limits

• Example– blood glucose level is kept within narrow range

Control of Homeostasis

• Homeostasis is continually being disrupted by– external stimuli or

• intense heat, cold , and lack of oxygen

– internal stimuli• psychological stresses

• exercise

• Disruptions are usually mild & temporary

• If homeostasis is not maintained, death may result

Neural and Endocrine Controls

• Process of maintaining a controlled condition– sensory receptors detect change in a monitored variable– nervous system and/or endocrine system responds

• Example of control of blood gas level– exercise increases blood CO2 levels– sensory receptors detect change– nervous system increases heart and breathing rates to

remove excess CO2– adrenal gland releases epinephrine to increase heart and

breathing rates

Components of Feedback Loop• Receptor

– monitors a controlled condition

• Control center

– determines next action

• Effector– receives directions from the control

center

– produces a response that changes the controlled condition

Negative & Positive Feedback Loops

• Negative feedback loop– original stimulus reversed – most feedback systems in the body are negative– used for conditions that need frequent adjustment– body temperature, blood sugar levels, blood

pressure

• Positive feedback loop– original stimulus intensified– seen during normal childbirth

Homeostasis of Blood Pressure• Pressure receptors in walls of

certain arteries detect an increase in BP– blood Pressure = force of blood

on walls of vessels

• Brain receives input and signals heart and blood vessels

• Heart rate slows and arterioles dilate (increase in diameter)

• BP returns to normal

Positive Feedback during Childbirth• Stretch receptors in walls of

uterus send signals to the brain

• Brain releases hormone (oxytocin) into bloodstream

• Uterine smooth muscle contracts more forcefully

• More stretch, more hormone, more contraction etc.

• Cycle ends with birth of the baby & decrease in stretch

Basic Anatomical Terminology

• Anatomical position

• Regions of the body

• Anatomical planes, sections and directional

terms

Anatomical Position• Standardized position from which to

describe directional terms– standing upright

– facing the observer, head level

– eyes facing forward

– feet flat on the floor

– arms at the sides

– palms turned forward

• Prone position = lying face down• Supine position = lying face up

anatomical position?

Common Regional Names

• Clinical terminology based on a Greek or Latin root word.

Planes and Sections

• A plane is an imaginary flat surface that passes through the body.

• A section is one of the 2 surfaces (pieces) that results when the body is cut by a plane passing through it.

Sagittal Plane

• Sagittal plane– divides the body or an

organ into left and right sides

• Midsagittal plane– produces equal halves

• Parasagittal plane– produces unequal

halves

Other Planes and Sections• Frontal or coronal plane

– divides the body or an organ into front (anterior) and back (posterior) portions

• Transverse(cross-sectional) or horizontal plane– divides the body or an organ into upper

(superior) or lower (inferior) portions

• Oblique plane– some combination of 2 other planes

Planes and Sections of the Brain(3-D anatomical relationships revealed)

• Horizontal Plane

• Frontal Plane

• Midsagittal Plane

Major Directional Terms

• Dorsal or Posterior– at the back of the body

– The brain is posterior to the forehead.

• Ventral or Anterior– at the front of the body

– The sternum is anterior to the heart.

Dorsal or Ventral

Dorsal Body Cavity• Near dorsal surface of

body

• 2 subdivisions– cranial cavity

• holds the brain

• formed by skull

– vertebral or spinal canal• contains the spinal cord

• formed by vertebral column

Ventral Body Cavity• Near ventral surface of

body• 2 subdivisions

– thoracic cavity above diaphragm

– abdominopelvic cavity below diaphragm

• Diaphragm = large, dome-shaped muscle

• Organs called viscera

Abdominopelvic Cavity

• Inferior portion of ventral body cavity below diaphragm• Encircled by abdominal wall, bones & muscles of pelvis

Thoracic Cavity

• Encircled by ribs, sternum, vertebral column and muscle• Divided into 2 pleural cavities by mediastinum • Mediastinum contains all thoracic organs except lungs

Mediastinum

• Midline wall of tissue that contains heart and great vessels, esophagus, trachea and thymus.

Serous Membranes

• Thin slippery membrane lines body cavities not open to the outside– parietal layer lines walls of cavities– visceral layer covers viscera within the cavities

• Serous fluid reduces friction

Pleural & Pericardial Cavities

• Visceral pleura clings to surface of lungs --- Parietal pleura lines chest wall

• Visceral pericardium covers heart --- Parietal pericardium lines pericardial sac

Peritoneum

• Visceral peritoneum --- serous membrane that covers the abdominal viscera

• Parietal peritoneum --- serous membrane that lines the abdominal wall